@Sodbury You are correct. The browser you use and the settings you set it to determine if your location is included. It's very hard, though, to keep that rough location a secret permanently unless you use some kind of remote server to present your presences to the Internet. They come in several flavors. VPN (Virtual Private Nework) is the most common. Using it you go through the VPN server and anything you send out should hide your original IP address. So, if the server is in New York and you are in California and you request something form some X website it should think you are in New York, or, usually, knowing it's a VPN server, that it doesn't know where you are. "Obfuscated" VPN also hides that you are using a VPN. You can also use a TOR server (can't remember what TOR stands for), but it sends your data through a whole bunch of servers, each independent of each other and run by volunteers, and thus "scrambles" the route until nobody knows from where the original came except for each "hop" along the way. And since each request is randomly routed, it's pretty hard to figure it all out.
A second set of ways works temporarily. You can ask your ISP for a different IP address. Since the IP address of your router (the "gateway" to the internet) is "public" in that it is necessary for the Internet to know it if it is to communicate with you, the physical location gets "known" in various ways pretty quickly. But it takes some time. So you can try to have your ISP change that number. It used to be if you just unplugged the router and then plugged it in a again you would get a different number...though it was usually so close to the original it took far less time to figure the approximate physical location... but now ISP's pretty much assign static addresses to their equipment. Not all of them do, but the big players, I find, do so. Still, it might be worth a shot. Another way is to join a different network. Your company probably has different networks for different things, and if you talk nicely to the IT department they might move you. But if they are that sophisticated you are probably using a VPN server anyway. Any targeted ads, in that case, are because you live close to the building that contains the VPN servers.
Third, a sort of hybrid set. You can use a NAT firewall. It's not a firewall so much as a firewall going through a NAT server. All the devices connected share a single public address, so if you are far enough away from the NAT server (like VPN) you won't get the localized adds. Sort of like VPN but without the need to log into a VPN server. Or you could try to use more sophisticated tools that scramble, hide, or other wise make it difficult to find your IP address, but to do so you really need to know what you are doing lest you end up with no Internet at all and/or an ISP with a bad attitude toward you.
If you've noticed, all this relies on changing your "Public" address. That address is necessary to route things back to you. All the methods named above are there to make it appear you are not where you are. And that's one way to keep things private. There are, to this explanation, a lot of "caveats" and "more complicated and thus more accurate" explanations, but this will have to do for now.
AJ